As inkjet recording methods, they are known methods including an actuator driven method represented by a piezoelectric inkjet recording method and a heating and film boiling method represented by a thermal inkjet recording method. In any method, in accordance with image data to be printed, ink is ejected from a nozzle of a recording head so that the image data are formed. When compared with the electrophotographic recording method, the inkjet recording method can be implemented easier; therefore, the inkjet recording method is applied in various image forming apparatuses such as a printer, a facsimile machine, a copier and the like.
As a main part of an imaging engine, such an image forming apparatus includes a recording head having a nozzle from which ink is ejected. If a process that the ink ejected from the nozzle of the recording head is printed on a recording paper is performed near the recording head, paper powder from the recording paper or dust is more likely to be adhered to the nozzle. As a result, a flying direction of the ink may deviate from a desired flying direction and/or the nozzle may be clogged due to the paper powder or dust; thereby degrading a quality of printed image and reducing the reliability of printing. Further, from the viewpoints of emission stability, a low-viscosity ink is generally used. However, when such a low-viscosity ink is used, bleeding of ink (ink bleeding) is more likely to occur when the ink is deposited on the surface of the recording paper.
To avoid the problem, there is a known method employed in which an intermediate transfer body is provided on which ink image is formed with the ink ejected from the nozzle of the recording head so that the formed ink image on the intermediate transfer body is separately transferred to a recording medium.
Patent Document 1 discloses an image forming apparatus including a treatment liquid application unit applying a treatment liquid for changing a pH of ink onto an intermediate transfer body, an ink application unit applying ink onto the treatment liquid on the intermediate transfer body, and a transfer unit transferring an image formed on the intermediate transfer body to a recording medium. In this case, in the ink, at least a pigment and polymer fine particles are dispersed in a medium including water and a water-soluble solution; and the pigment and the polymer fine particles are aggregated by changing the pH of the ink. However, in this method, it is always required to apply a treatment liquid to aggregate the pigment in the ink, which becomes necessary to add a device for applying the treatment liquid and may reduce a printing speed.
Patent Document 1: Japanese Patent Application Publication No. 2008-62397